1. Field of the Invention
The present invention relates to a combination smoke and heat detector.
2. Description of the Related Art
Conventionally, a combination smoke and heat detector is normally installed on an indoor ceiling and the like, and includes a temperature detection means for detecting air temperature, a smoke detection means for detecting smoke in the air, and a determination means for determining whether or not a fire has occurred on the basis of the detection results of those means. Further, the combination smoke and heat detector includes an “indication lamp” that blinks to indicate that the combination smoke and heat detector is in a normal operational state, or lights up to indicate that the combination smoke and heat detector has detected the occurrence of a fire.
In the combination smoke and heat detector, a printed circuit board which is provided with the determination means is mounted in a cylindrical body base. The printed circuit board is provided with the temperature detection means and the smoke detection means. The temperature detection means includes a thermosensitive element such as a thermistor, and detects temperature at the leading end thereof. The smoke detection means includes light-emitting elements and light-receiving elements arranged in a dark chamber, and detects the presence/absence or the extent of light scattering, which is caused by smoke particles. The dark chamber is mounted to the printed circuit board, and surrounded by a light-shieldable and ventilatable labyrinth body.
In addition, the printed circuit board is accommodated in a protective cover in which an opening portion for allowing the dark chamber to protrude therein and a through-hole for allowing the thermistor to pass therethrough are formed. The range in which the dark chamber and the thermistor protrude with respect to the protective cover is protected by a protector (refer to pages 3 to 4 and FIG. 1 of Japanese Patent Application Laid-open No. Hei 09-091559, for example).
However, in the invention disclosed in Japanese Patent Application Laid-open No. Hei 09-091559, in the case of mounting the indication lamp (LED chip, for example) to the printed circuit board, even when the protective cover is provided with a visual confirmation window, light emitted from the indication lamp can be visually confirmed only in a particular direction on the straight line coupling the indication lamp and the protective cover with each other, and cannot be visually confirmed out of the direction. Thus, there are problems of inconvenience and rise in cost due to increases in the number of components and in structural complexity.
Meanwhile, even when the indication lamp is raised up (separated) from the printed circuit board so as to partially protrude from a through-hole formed in the protective cover, light emitted from the indication lamp is shielded by the dark chamber protruding from the protective cover. As a result, the direction in which the light can be visually confirmed is limited, which leads to inconvenience.
Further, in the invention disclosed in Japanese Patent Application Laid-open No. Hei 09-091559, although the thermistor protrudes from the protective cover 30, the protruding side thereof is covered with the protector. In addition, although a vent hole is formed at a position of the protector, which corresponds to the thermistor, only a part of the air (including smoke) flowing along the surface of the protector intrudes into the vent hole, and most of the air flows along the surface of the protector without intruding into the vent hole. Thus, it is difficult to capture air (thermal currents) from the direction in which the dark chamber is sandwiched, and there is a problem that the temperature of the air, as described above, cannot be satisfactorily measured.